1. Field of the Invention
The present invention relates to a heat exchanger which is used for an air conditioner.
2. Description of the Related Art
FIGS. 7 to 14 show examples of structures of heat exchangers which are used as evaporators for vehicular air conditioners and the like. The heat exchangers shown in these figures are called drawn-cup type heat exchangers, and each air conditioner is constructed by alternately overlaying plate shaped refrigerant passage portions and corrugated plate shaped cooling fins.
In FIGS. 7 and 8, reference numeral 11 denotes the refrigerant flow portions and reference numeral 12 denotes the cooling fins. The refrigerant flow portion 11 is obtained by overlaying substantially rectangular flat plates 13 and 14 which are formed by drawing, and brazing at the outer peripheral portions and the central portions thereof. A refrigerant inlet 15 and a refrigerant outlet 16 are provided side by side at the lower end part of the refrigerant flow portion 11, and an inverted U-shaped refrigerant flow path R which extends upwardly from the refrigerant inlet 15 and turns downwards at the top of the refrigerant flow portion 11 toward the refrigerant outlet 16, is formed within the refrigerant flow portion 11.
A plurality of dimples 17 are formed in the refrigerant flow portion 11 by denting the flat plates 13 and 14 which form the refrigerant flow path R from the outside, and these dimples 17 form a plurality of bulged portions 18 in the refrigerant flow path R. Furthermore, the left end of the laminated refrigerant flow portions 11 and cooling fins 12 are covered by a side plate 19. Hereinafter, the left end of each figure is referred to as the xe2x80x9cproximal endxe2x80x9d and the right end of each Figure is referred to xe2x80x9cdistal endxe2x80x9d.
The refrigerant inlet 15 is composed of opening portions 13a and 14a formed in the flat plates 13 and 14, and the refrigerant inlets 15 of the respective refrigerant flow portions 11 are directly overlaid with no intervening cooling fin 12, so that a continuous space Sa is formed. Similarly, the refrigerant outlet 16 is composed of opening portions 13a and 14a formed in the flat plates 13 and 14, and the refrigerant outlets 16 of the respective refrigerant flow portions 11 are directly overlaid with no intervening cooling fins 12, so that a continuous space Sb is formed. The proximal end of the space Sa is connected with a refrigerant inlet pipe 20 which extends from the central part of the height of the heat exchanger, and the proximal end of the space Sb is connected with a refrigerant outlet pipe 21. Furthermore, the distal end of each space Sa, Sb is closed by a cover which is not shown in Figures.
In this heat exchanger, refrigerant which flows into the space Sa through the refrigerant inlet pipe 20 is distributed to each of the refrigerant flow paths R, undergoes heat exchange while it passes through the refrigerant flow paths R, and then is collected at the space Sb and exits from the refrigerant outlet pipe 21.
The heat exchanger shown in FIGS. 9 to 11 provides the refrigerant inlet 15 and the refrigerant outlet 16 at the upper end part of the refrigerant flow portion 11, and a U-shaped refrigerant flow path R which extends downwards from the refrigerant inlet 15 and turns upwards at the bottom of the refrigerant flow portion 11 towards the refrigerant outlet 16 is formed within the refrigerant flow portion 11. Furthermore, in this air conditioner, the bulged portions 18 are not provided, and a corrugated inner fin 18a is sandwiched between each of the flat plates 13 and 14. In addition, the proximal end of the space Sa is connected with the refrigerant inlet pipe 20 via a header 22, and the distal end of the space Sb is connected with the refrigerant outlet pipe 21 via a header 23.
In this heat exchanger, refrigerant which flows into the space Sa from the refrigerant inlet pipe 20 through the header 22 is distributed to each of the refrigerant flow paths R, undergoes heat exchange while passing through the refrigerant flow path R, and then is collected at the space Sb and exists from the refrigerant outlet pipe 21.
The heat exchanger shown in FIGS. 12 to 14 further provides an opening 24 which opens adjacent to each refrigerant inlet 15 and refrigerant outlet 16, and the openings 24 of the refrigerant flow portions 11 are overlaid with no intervening cooling fins 12 so that a continuous space (forward flow path) Sc is formed. Further, the space Sa is divided into two spaces Sa-1 and Sa-2 in the longitudinal direction by a partitioning wall 25. Furthermore, a cover 26 is fixed on the distal end of the heat exchanger, so that a turning portion 27 which connects the distal ends of spaces Sc and Sa-1 is formed by the cover 26. In addition, the proximal end of the space Sc is connected with the refrigerant inlet pipe 20 and the proximal end of the space Sa is connected with the refrigerant outlet pipe 21, and both ends of the space Sb are closed by covers 28.
In this heat exchanger, the flow of the refrigerant which flows into the space Sc through the refrigerant inlet pipe 20 is turned at the turning portion 27 and flows into the space Sa-1 and is distributed to the refrigerant flow portions 11 at the distal end side of the heat exchanger. The refrigerant undergoes heat exchange while it passes through each of the refrigerant flow paths R, and is collected at the space Sb. The refrigerant is further distributed to the refrigerant flow portions 11 at the proximal end side of the heat exchanger and passes through each refrigerant flow path R, and is collected at the space Sa-2, and then, the refrigerant exists from the refrigerant outlet pipe 21.
However, when the refrigerant inlet pipe 20 has a 90 degree curve adjacent to the space Sa as denoted by symbol A in FIG. 7 for example, the flow of the refrigerant is slowed down due to the curve, and therefore, the refrigerant may not reach the innermost regions (the distal end part) of the space Sa, and the refrigerant may not flow to the distal end part of the space Sa. As a result, the refrigerant may not be uniformly distributed throughout the respective refrigerant flow paths R, and consequently, the problem that heat exchange is not sufficient at the refrigerant flow paths R at the distal end part may occur.
Furthermore, the heat exchangers as described above are manufactured by braze welding. For example, in the heat exchanger shown in FIGS. 10 and 11, the refrigerant flow portion 11 is constructed by brazing the flat plates 13 and 14 at flange portions 13c and 14c which are provided on the outer peripheral portions thereof as shown in FIG. 11. In addition, adjacent refrigerant inlets 15 (or refrigerant outlets 16) are fastened by brazing a flange-shaped side wall 13d which is formed at each opening portion 13a (or 14b) and a flange-shaped side wall 14d which is formed at adjacent opening portion 14a (or 13b). However, in the latter case, the fastening positions of the refrigerant inlets 15 or refrigerant outlets 16 protrude into the space Sa or Sb and give rise to resistance to the flow of fluid (refrigerant) in the space Sa or Sb. As a result, the pressure loss of the fluid which passes the space Sa or Sb caused by the resistance increases to a significant level, and the heat exchange capacity of the heat exchanger decreases.
Moreover, in recent years, the cooling fins 12 and flat plates 13, 14 have become thinner, in compliance with the demand for reducing the weight and size of the heat exchanger. However, in case of the heat exchanger as shown in FIGS. 12 to 14, it is difficult to reduce the thickness of the turning portion 27 which receives the pressure of the flow of the refrigerant without reducing its strength.
The present invention was made in consideration of the above-mentioned circumstances, and a first object of the present invention is to uniformly distribute the refrigerant in the space Sa and improve the heat exchange capacity of the heat exchanger. Further, a second object of the present invention is to reduce the pressure loss of the refrigerant in the space Sa or Sb and improve the heat exchange capacity of the heat exchanger. Furthermore, a third object of the present invention is to provide the heat exchanger with a reduced weight and a minimized size while maintaining the strength of the turning portion 27.
The present invention relates to a heat exchanger in which a plate-shaped refrigerant flow portion which provides an internal refrigerant flow path by overlaying two flat plates formed by drawing and a cooling fin are alternately layered; comprising an opening portion provided on each of the flat plates and which is connected with the refrigerant flow path, and a continuous space for the flow of the refrigerant which is provided by connecting the opening portions of adjacent refrigerant flow portions; wherein the refrigerant which flows in the space is distributed to the respective refrigerant flow paths through the opening portions.
Particularly, the heat exchanger of the present invention is characterized by comprising a means for improving the heat exchange capacity. This means is a narrowing means which is provided at an upstream end part of the space in order to uniformly distribute the refrigerant to the respective refrigerant flow paths, for example.
In this case, it is preferable to provide a rectifier which rectifies the flow of the refrigerant along the longitudinal direction of the space at a downstream end side of the space, and it is further preferable to provide the rectifier adjacent to the narrowing means.
A tubular portion which projects substantially perpendicularly to the flat plates may be provided at each of the opening portions of the respective refrigerant flow portions as the means for improving the heat exchange capacity. The tubular portion which is provided at one of the refrigerant flow portions is inserted into the tubular portion of the adjacent refrigerant flow portion so as to closely seal the outer and inner peripheral surface of these tubular portions.
In this case, it is preferable that the diameter of an end part of the tubular portion of the adjacent refrigerant flow portion has a uniform diameter which is larger than that of the inserted tubular portion, or to have a diameter which is gradually enlarged in the longitudinal direction so as to be larger than that of the inserted tubular portion.
Furthermore, the present invention is also characterized by comprising a forward flow path in which the refrigerant flows from the proximal end of the heat exchanger to the distal end thereof, and a turning portion which is provided at the distal end and the direction of flow of the refrigerant which flows from the forward flow path to the space; wherein the turning portion is a concave portion which is formed on a plate member which overlays the distal end surface of the heat exchanger, and a back surface of the turning portion is supported by a side plate which overlays the distal end surface of the plate member.
In this case, it is preferable that the turning portion has a center portion which forms a flat surface and a peripheral portion which forms a curved surface which smoothly continues from the center portion, and it is further preferable that a plurality of projecting portions which project along the direction of the thickness of the plate member are formed on the peripheral portion.